[S390] take mmap_sem when walking guest page table
gmap_fault needs to walk the guest page table. However, parts of
that may change if some other thread does munmap. In that case
gmap_unmap_notifier will also unmap the corresponding parts from
the guest page table. We need to take mmap_sem in order to serialize
these operations.
do_exception now calls __gmap_fault with mmap_sem held which does
not get exported to modules. The exported function, which is called
from KVM, now takes mmap_sem.
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index c0cb794..bc5f520 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -696,6 +696,7 @@
int gmap_map_segment(struct gmap *gmap, unsigned long from,
unsigned long to, unsigned long length);
int gmap_unmap_segment(struct gmap *gmap, unsigned long to, unsigned long len);
+unsigned long __gmap_fault(unsigned long address, struct gmap *);
unsigned long gmap_fault(unsigned long address, struct gmap *);
/*
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index de3af0c..1766def 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -307,7 +307,7 @@
#ifdef CONFIG_PGSTE
if (test_tsk_thread_flag(current, TIF_SIE) && S390_lowcore.gmap) {
- address = gmap_fault(address,
+ address = __gmap_fault(address,
(struct gmap *) S390_lowcore.gmap);
if (address == -EFAULT) {
fault = VM_FAULT_BADMAP;
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 96e85ac..441d344 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -393,7 +393,10 @@
}
EXPORT_SYMBOL_GPL(gmap_map_segment);
-unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
+/*
+ * this function is assumed to be called with mmap_sem held
+ */
+unsigned long __gmap_fault(unsigned long address, struct gmap *gmap)
{
unsigned long *table, vmaddr, segment;
struct mm_struct *mm;
@@ -461,7 +464,17 @@
return vmaddr | (address & ~PMD_MASK);
}
return -EFAULT;
+}
+unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
+{
+ unsigned long rc;
+
+ down_read(&gmap->mm->mmap_sem);
+ rc = __gmap_fault(address, gmap);
+ up_read(&gmap->mm->mmap_sem);
+
+ return rc;
}
EXPORT_SYMBOL_GPL(gmap_fault);